git.sesse.net Git - ffmpeg/blob - libavformat/tls_schannel.c

   1 /*
   2  * Copyright (c) 2015 Hendrik Leppkes
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 /** Based on the CURL SChannel module */
  22
  23 #include "avformat.h"
  24 #include "internal.h"
  25 #include "network.h"
  26 #include "os_support.h"
  27 #include "url.h"
  28 #include "tls.h"
  29
  30 #define SECURITY_WIN32
  31 #include <windows.h>
  32 #include <security.h>
  33 #include <schnlsp.h>
  34
  35 #define SCHANNEL_INITIAL_BUFFER_SIZE   4096
  36 #define SCHANNEL_FREE_BUFFER_SIZE      1024
  37
  38 /* mingw does not define this symbol */
  39 #ifndef SECBUFFER_ALERT
  40 #define SECBUFFER_ALERT                17
  41 #endif
  42
  43 typedef struct TLSContext {
  44     const AVClass *class;
  45     TLSShared tls_shared;
  46
  47     CredHandle cred_handle;
  48     TimeStamp cred_timestamp;
  49
  50     CtxtHandle ctxt_handle;
  51     TimeStamp ctxt_timestamp;
  52
  53     ULONG request_flags;
  54     ULONG context_flags;
  55
  56     uint8_t *enc_buf;
  57     int enc_buf_size;
  58     int enc_buf_offset;
  59
  60     uint8_t *dec_buf;
  61     int dec_buf_size;
  62     int dec_buf_offset;
  63
  64     SecPkgContext_StreamSizes sizes;
  65
  66     int connected;
  67     int connection_closed;
  68     int sspi_close_notify;
  69 } TLSContext;
  70
  71 static void init_sec_buffer(SecBuffer *buffer, unsigned long type,
  72                             void *data, unsigned long size)
  73 {
  74     buffer->cbBuffer   = size;
  75     buffer->BufferType = type;
  76     buffer->pvBuffer   = data;
  77 }
  78
  79 static void init_sec_buffer_desc(SecBufferDesc *desc, SecBuffer *buffers,
  80                                  unsigned long buffer_count)
  81 {
  82     desc->ulVersion = SECBUFFER_VERSION;
  83     desc->pBuffers = buffers;
  84     desc->cBuffers = buffer_count;
  85 }
  86
  87 static int tls_shutdown_client(URLContext *h)
  88 {
  89     TLSContext *c = h->priv_data;
  90     TLSShared *s = &c->tls_shared;
  91     int ret;
  92
  93     if (c->connected) {
  94         SecBufferDesc BuffDesc;
  95         SecBuffer Buffer;
  96         SECURITY_STATUS sspi_ret;
  97         SecBuffer outbuf;
  98         SecBufferDesc outbuf_desc;
  99
 100         DWORD dwshut = SCHANNEL_SHUTDOWN;
 101         init_sec_buffer(&Buffer, SECBUFFER_TOKEN, &dwshut, sizeof(dwshut));
 102         init_sec_buffer_desc(&BuffDesc, &Buffer, 1);
 103
 104         sspi_ret = ApplyControlToken(&c->ctxt_handle, &BuffDesc);
 105         if (sspi_ret != SEC_E_OK)
 106             av_log(h, AV_LOG_ERROR, "ApplyControlToken failed\n");
 107
 108         init_sec_buffer(&outbuf, SECBUFFER_EMPTY, NULL, 0);
 109         init_sec_buffer_desc(&outbuf_desc, &outbuf, 1);
 110
 111         sspi_ret = InitializeSecurityContext(&c->cred_handle, &c->ctxt_handle, s->host,
 112                                              c->request_flags, 0, 0, NULL, 0, &c->ctxt_handle,
 113                                              &outbuf_desc, &c->context_flags, &c->ctxt_timestamp);
 114         if (sspi_ret == SEC_E_OK || sspi_ret == SEC_I_CONTEXT_EXPIRED) {
 115             ret = ffurl_write(s->tcp, outbuf.pvBuffer, outbuf.cbBuffer);
 116             FreeContextBuffer(outbuf.pvBuffer);
 117             if (ret < 0 || ret != outbuf.cbBuffer)
 118                 av_log(h, AV_LOG_ERROR, "Failed to send close message\n");
 119         }
 120
 121         c->connected = 0;
 122     }
 123     return 0;
 124 }
 125
 126 static int tls_close(URLContext *h)
 127 {
 128     TLSContext *c = h->priv_data;
 129
 130     tls_shutdown_client(h);
 131
 132     DeleteSecurityContext(&c->ctxt_handle);
 133     FreeCredentialsHandle(&c->cred_handle);
 134
 135     av_freep(&c->enc_buf);
 136     c->enc_buf_size = c->enc_buf_offset = 0;
 137
 138     av_freep(&c->dec_buf);
 139     c->dec_buf_size = c->dec_buf_offset = 0;
 140
 141     ffurl_closep(&c->tls_shared.tcp);
 142     return 0;
 143 }
 144
 145 static int tls_client_handshake_loop(URLContext *h, int initial)
 146 {
 147     TLSContext *c = h->priv_data;
 148     TLSShared *s = &c->tls_shared;
 149     SECURITY_STATUS sspi_ret;
 150     SecBuffer outbuf[3] = { 0 };
 151     SecBufferDesc outbuf_desc;
 152     SecBuffer inbuf[2];
 153     SecBufferDesc inbuf_desc;
 154     int i, ret = 0, read_data = initial;
 155
 156     if (c->enc_buf == NULL) {
 157         c->enc_buf_offset = 0;
 158         ret = av_reallocp(&c->enc_buf, SCHANNEL_INITIAL_BUFFER_SIZE);
 159         if (ret < 0)
 160             goto fail;
 161         c->enc_buf_size = SCHANNEL_INITIAL_BUFFER_SIZE;
 162     }
 163
 164     if (c->dec_buf == NULL) {
 165         c->dec_buf_offset = 0;
 166         ret = av_reallocp(&c->dec_buf, SCHANNEL_INITIAL_BUFFER_SIZE);
 167         if (ret < 0)
 168             goto fail;
 169         c->dec_buf_size = SCHANNEL_INITIAL_BUFFER_SIZE;
 170     }
 171
 172     while (1) {
 173         if (c->enc_buf_size - c->enc_buf_offset < SCHANNEL_FREE_BUFFER_SIZE) {
 174             c->enc_buf_size = c->enc_buf_offset + SCHANNEL_FREE_BUFFER_SIZE;
 175             ret = av_reallocp(&c->enc_buf, c->enc_buf_size);
 176             if (ret < 0) {
 177                 c->enc_buf_size = c->enc_buf_offset = 0;
 178                 goto fail;
 179             }
 180         }
 181
 182         if (read_data) {
 183             ret = ffurl_read(c->tls_shared.tcp, c->enc_buf + c->enc_buf_offset,
 184                              c->enc_buf_size - c->enc_buf_offset);
 185             if (ret < 0) {
 186                 av_log(h, AV_LOG_ERROR, "Failed to read handshake response\n");
 187                 goto fail;
 188             }
 189             c->enc_buf_offset += ret;
 190         }
 191
 192         /* input buffers */
 193         init_sec_buffer(&inbuf[0], SECBUFFER_TOKEN, av_malloc(c->enc_buf_offset), c->enc_buf_offset);
 194         init_sec_buffer(&inbuf[1], SECBUFFER_EMPTY, NULL, 0);
 195         init_sec_buffer_desc(&inbuf_desc, inbuf, 2);
 196
 197         if (inbuf[0].pvBuffer == NULL) {
 198             av_log(h, AV_LOG_ERROR, "Failed to allocate input buffer\n");
 199             ret = AVERROR(ENOMEM);
 200             goto fail;
 201         }
 202
 203         memcpy(inbuf[0].pvBuffer, c->enc_buf, c->enc_buf_offset);
 204
 205         /* output buffers */
 206         init_sec_buffer(&outbuf[0], SECBUFFER_TOKEN, NULL, 0);
 207         init_sec_buffer(&outbuf[1], SECBUFFER_ALERT, NULL, 0);
 208         init_sec_buffer(&outbuf[2], SECBUFFER_EMPTY, NULL, 0);
 209         init_sec_buffer_desc(&outbuf_desc, outbuf, 3);
 210
 211         sspi_ret = InitializeSecurityContext(&c->cred_handle, &c->ctxt_handle, s->host, c->request_flags,
 212                                              0, 0, &inbuf_desc, 0, NULL, &outbuf_desc, &c->context_flags,
 213                                              &c->ctxt_timestamp);
 214         av_freep(&inbuf[0].pvBuffer);
 215
 216         if (sspi_ret == SEC_E_INCOMPLETE_MESSAGE) {
 217             av_log(h, AV_LOG_DEBUG, "Received incomplete handshake, need more data\n");
 218             read_data = 1;
 219             continue;
 220         }
 221
 222         /* remote requests a client certificate - attempt to continue without one anyway */
 223         if (sspi_ret == SEC_I_INCOMPLETE_CREDENTIALS &&
 224             !(c->request_flags & ISC_REQ_USE_SUPPLIED_CREDS)) {
 225             av_log(h, AV_LOG_VERBOSE, "Client certificate has been requested, ignoring\n");
 226             c->request_flags |= ISC_REQ_USE_SUPPLIED_CREDS;
 227             read_data = 0;
 228             continue;
 229         }
 230
 231         /* continue handshake */
 232         if (sspi_ret == SEC_I_CONTINUE_NEEDED || sspi_ret == SEC_E_OK) {
 233             for (i = 0; i < 3; i++) {
 234                 if (outbuf[i].BufferType == SECBUFFER_TOKEN && outbuf[i].cbBuffer > 0) {
 235                     ret = ffurl_write(c->tls_shared.tcp, outbuf[i].pvBuffer, outbuf[i].cbBuffer);
 236                     if (ret < 0 || ret != outbuf[i].cbBuffer) {
 237                         av_log(h, AV_LOG_VERBOSE, "Failed to send handshake data\n");
 238                         ret = AVERROR(EIO);
 239                         goto fail;
 240                     }
 241                 }
 242
 243                 if (outbuf[i].pvBuffer != NULL) {
 244                     FreeContextBuffer(outbuf[i].pvBuffer);
 245                     outbuf[i].pvBuffer = NULL;
 246                 }
 247             }
 248         } else {
 249             if (sspi_ret == SEC_E_WRONG_PRINCIPAL)
 250                 av_log(h, AV_LOG_ERROR, "SNI or certificate check failed\n");
 251             else
 252                 av_log(h, AV_LOG_ERROR, "Creating security context failed (0x%lx)\n", sspi_ret);
 253             ret = AVERROR_UNKNOWN;
 254             goto fail;
 255         }
 256
 257         if (inbuf[1].BufferType == SECBUFFER_EXTRA && inbuf[1].cbBuffer > 0) {
 258             if (c->enc_buf_offset > inbuf[1].cbBuffer) {
 259                 memmove(c->enc_buf, (c->enc_buf + c->enc_buf_offset) - inbuf[1].cbBuffer,
 260                         inbuf[1].cbBuffer);
 261                 c->enc_buf_offset = inbuf[1].cbBuffer;
 262                 if (sspi_ret == SEC_I_CONTINUE_NEEDED) {
 263                     read_data = 0;
 264                     continue;
 265                 }
 266             }
 267         } else {
 268             c->enc_buf_offset  = 0;
 269         }
 270
 271         if (sspi_ret == SEC_I_CONTINUE_NEEDED) {
 272             read_data = 1;
 273             continue;
 274         }
 275
 276         break;
 277     }
 278
 279     return 0;
 280
 281 fail:
 282     /* free any remaining output data */
 283     for (i = 0; i < 3; i++) {
 284         if (outbuf[i].pvBuffer != NULL) {
 285             FreeContextBuffer(outbuf[i].pvBuffer);
 286             outbuf[i].pvBuffer = NULL;
 287         }
 288     }
 289
 290     return ret;
 291 }
 292
 293 static int tls_client_handshake(URLContext *h)
 294 {
 295     TLSContext *c = h->priv_data;
 296     TLSShared *s = &c->tls_shared;
 297     SecBuffer outbuf;
 298     SecBufferDesc outbuf_desc;
 299     SECURITY_STATUS sspi_ret;
 300     int ret;
 301
 302     init_sec_buffer(&outbuf, SECBUFFER_EMPTY, NULL, 0);
 303     init_sec_buffer_desc(&outbuf_desc, &outbuf, 1);
 304
 305     c->request_flags = ISC_REQ_SEQUENCE_DETECT | ISC_REQ_REPLAY_DETECT |
 306                        ISC_REQ_CONFIDENTIALITY | ISC_REQ_ALLOCATE_MEMORY |
 307                        ISC_REQ_STREAM;
 308
 309     sspi_ret = InitializeSecurityContext(&c->cred_handle, NULL, s->host, c->request_flags, 0, 0,
 310                                          NULL, 0, &c->ctxt_handle, &outbuf_desc, &c->context_flags,
 311                                          &c->ctxt_timestamp);
 312     if (sspi_ret != SEC_I_CONTINUE_NEEDED) {
 313         av_log(h, AV_LOG_ERROR, "Unable to create initial security context (0x%lx)\n", sspi_ret);
 314         ret = AVERROR_UNKNOWN;
 315         goto fail;
 316     }
 317
 318     ret = ffurl_write(s->tcp, outbuf.pvBuffer, outbuf.cbBuffer);
 319     FreeContextBuffer(outbuf.pvBuffer);
 320     if (ret < 0 || ret != outbuf.cbBuffer) {
 321         av_log(h, AV_LOG_ERROR, "Failed to send initial handshake data\n");
 322         ret = AVERROR(EIO);
 323         goto fail;
 324     }
 325
 326     return tls_client_handshake_loop(h, 1);
 327
 328 fail:
 329     DeleteSecurityContext(&c->ctxt_handle);
 330     return ret;
 331 }
 332
 333 static int tls_open(URLContext *h, const char *uri, int flags, AVDictionary **options)
 334 {
 335     TLSContext *c = h->priv_data;
 336     TLSShared *s = &c->tls_shared;
 337     SECURITY_STATUS sspi_ret;
 338     SCHANNEL_CRED schannel_cred = { 0 };
 339     int ret;
 340
 341     if ((ret = ff_tls_open_underlying(s, h, uri, options)) < 0)
 342         goto fail;
 343
 344     if (s->listen) {
 345         av_log(h, AV_LOG_ERROR, "TLS Listen Sockets with SChannel is not implemented.\n");
 346         ret = AVERROR(EINVAL);
 347         goto fail;
 348     }
 349
 350     /* SChannel Options */
 351     schannel_cred.dwVersion = SCHANNEL_CRED_VERSION;
 352
 353     if (s->verify)
 354         schannel_cred.dwFlags = SCH_CRED_AUTO_CRED_VALIDATION |
 355                                 SCH_CRED_REVOCATION_CHECK_CHAIN;
 356     else
 357         schannel_cred.dwFlags = SCH_CRED_MANUAL_CRED_VALIDATION |
 358                                 SCH_CRED_IGNORE_NO_REVOCATION_CHECK |
 359                                 SCH_CRED_IGNORE_REVOCATION_OFFLINE;
 360
 361     /* Get credential handle */
 362     sspi_ret = AcquireCredentialsHandle(NULL, (TCHAR *)UNISP_NAME, SECPKG_CRED_OUTBOUND,
 363                                         NULL,  &schannel_cred, NULL, NULL, &c->cred_handle,
 364                                         &c->cred_timestamp);
 365     if (sspi_ret != SEC_E_OK) {
 366         av_log(h, AV_LOG_ERROR, "Unable to acquire security credentials (0x%lx)\n", sspi_ret);
 367         ret = AVERROR_UNKNOWN;
 368         goto fail;
 369     }
 370
 371     ret = tls_client_handshake(h);
 372     if (ret < 0)
 373         goto fail;
 374
 375     c->connected = 1;
 376
 377     return 0;
 378
 379 fail:
 380     tls_close(h);
 381     return ret;
 382 }
 383
 384 static int tls_read(URLContext *h, uint8_t *buf, int len)
 385 {
 386     TLSContext *c = h->priv_data;
 387     TLSShared *s = &c->tls_shared;
 388     SECURITY_STATUS sspi_ret = SEC_E_OK;
 389     SecBuffer inbuf[4];
 390     SecBufferDesc inbuf_desc;
 391     int size, ret;
 392     int min_enc_buf_size = len + SCHANNEL_FREE_BUFFER_SIZE;
 393
 394     /* If we have some left-over data from previous network activity,
 395      * return it first in case it is enough. It may contain
 396      * data that is required to know whether this connection
 397      * is still required or not, esp. in case of HTTP keep-alive
 398      * connections. */
 399     if (c->dec_buf_offset > 0)
 400         goto cleanup;
 401
 402     if (c->sspi_close_notify)
 403         goto cleanup;
 404
 405     if (!c->connection_closed) {
 406         size = c->enc_buf_size - c->enc_buf_offset;
 407         if (size < SCHANNEL_FREE_BUFFER_SIZE || c->enc_buf_size < min_enc_buf_size) {
 408             c->enc_buf_size = c->enc_buf_offset + SCHANNEL_FREE_BUFFER_SIZE;
 409             if (c->enc_buf_size < min_enc_buf_size)
 410                 c->enc_buf_size = min_enc_buf_size;
 411             ret = av_reallocp(&c->enc_buf, c->enc_buf_size);
 412             if (ret < 0) {
 413                 c->enc_buf_size = c->enc_buf_offset = 0;
 414                 return ret;
 415             }
 416         }
 417
 418         ret = ffurl_read(s->tcp, c->enc_buf + c->enc_buf_offset,
 419                          c->enc_buf_size - c->enc_buf_offset);
 420         if (ret == AVERROR_EOF) {
 421             c->connection_closed = 1;
 422             ret = 0;
 423         } else if (ret < 0) {
 424             av_log(h, AV_LOG_ERROR, "Unable to read from socket\n");
 425             return ret;
 426         }
 427
 428         c->enc_buf_offset += ret;
 429     }
 430
 431     while (c->enc_buf_offset > 0 && sspi_ret == SEC_E_OK) {
 432         /*  input buffer */
 433         init_sec_buffer(&inbuf[0], SECBUFFER_DATA, c->enc_buf, c->enc_buf_offset);
 434
 435         /* additional buffers for possible output */
 436         init_sec_buffer(&inbuf[1], SECBUFFER_EMPTY, NULL, 0);
 437         init_sec_buffer(&inbuf[2], SECBUFFER_EMPTY, NULL, 0);
 438         init_sec_buffer(&inbuf[3], SECBUFFER_EMPTY, NULL, 0);
 439         init_sec_buffer_desc(&inbuf_desc, inbuf, 4);
 440
 441         sspi_ret = DecryptMessage(&c->ctxt_handle, &inbuf_desc, 0, NULL);
 442         if (sspi_ret == SEC_E_OK || sspi_ret == SEC_I_RENEGOTIATE ||
 443             sspi_ret == SEC_I_CONTEXT_EXPIRED) {
 444             /* handle decrypted data */
 445             if (inbuf[1].BufferType == SECBUFFER_DATA) {
 446                 /* grow buffer if needed */
 447                 size = inbuf[1].cbBuffer > SCHANNEL_FREE_BUFFER_SIZE ?
 448                        inbuf[1].cbBuffer : SCHANNEL_FREE_BUFFER_SIZE;
 449                 if (c->dec_buf_size - c->dec_buf_offset < size || c->dec_buf_size < len)  {
 450                     c->dec_buf_size = c->dec_buf_offset + size;
 451                     if (c->dec_buf_size < len)
 452                         c->dec_buf_size = len;
 453                     ret = av_reallocp(&c->dec_buf, c->dec_buf_size);
 454                     if (ret < 0) {
 455                         c->dec_buf_size = c->dec_buf_offset = 0;
 456                         return ret;
 457                     }
 458                 }
 459
 460                 /* copy decrypted data to buffer */
 461                 size = inbuf[1].cbBuffer;
 462                 if (size) {
 463                     memcpy(c->dec_buf + c->dec_buf_offset, inbuf[1].pvBuffer, size);
 464                     c->dec_buf_offset += size;
 465                 }
 466             }
 467             if (inbuf[3].BufferType == SECBUFFER_EXTRA && inbuf[3].cbBuffer > 0) {
 468                 if (c->enc_buf_offset > inbuf[3].cbBuffer) {
 469                     memmove(c->enc_buf, (c->enc_buf + c->enc_buf_offset) - inbuf[3].cbBuffer,
 470                     inbuf[3].cbBuffer);
 471                     c->enc_buf_offset = inbuf[3].cbBuffer;
 472                 }
 473             } else
 474                 c->enc_buf_offset = 0;
 475
 476             if (sspi_ret == SEC_I_RENEGOTIATE) {
 477                 if (c->enc_buf_offset) {
 478                     av_log(h, AV_LOG_ERROR, "Cannot renegotiate, encrypted data buffer not empty\n");
 479                     ret = AVERROR_UNKNOWN;
 480                     goto cleanup;
 481                 }
 482
 483                 av_log(h, AV_LOG_VERBOSE, "Re-negotiating security context\n");
 484                 ret = tls_client_handshake_loop(h, 0);
 485                 if (ret < 0) {
 486                     goto cleanup;
 487                 }
 488                 sspi_ret = SEC_E_OK;
 489                 continue;
 490             } else if (sspi_ret == SEC_I_CONTEXT_EXPIRED) {
 491                 c->sspi_close_notify = 1;
 492                 if (!c->connection_closed) {
 493                     c->connection_closed = 1;
 494                     av_log(h, AV_LOG_VERBOSE, "Server closed the connection\n");
 495                 }
 496                 ret = 0;
 497                 goto cleanup;
 498             }
 499         } else if (sspi_ret == SEC_E_INCOMPLETE_MESSAGE) {
 500             ret = AVERROR(EAGAIN);
 501             goto cleanup;
 502         } else {
 503             av_log(h, AV_LOG_ERROR, "Unable to decrypt message (error 0x%x)\n", (unsigned)sspi_ret);
 504             ret = AVERROR(EIO);
 505             goto cleanup;
 506         }
 507     }
 508
 509     ret = 0;
 510
 511 cleanup:
 512     size = FFMIN(len, c->dec_buf_offset);
 513     if (size) {
 514         memcpy(buf, c->dec_buf, size);
 515         memmove(c->dec_buf, c->dec_buf + size, c->dec_buf_offset - size);
 516         c->dec_buf_offset -= size;
 517
 518         return size;
 519     }
 520
 521     if (ret == 0 && !c->connection_closed)
 522         ret = AVERROR(EAGAIN);
 523
 524     return ret < 0 ? ret : AVERROR_EOF;
 525 }
 526
 527 static int tls_write(URLContext *h, const uint8_t *buf, int len)
 528 {
 529     TLSContext *c = h->priv_data;
 530     TLSShared *s = &c->tls_shared;
 531     SECURITY_STATUS sspi_ret;
 532     int ret = 0, data_size;
 533     uint8_t *data = NULL;
 534     SecBuffer outbuf[4];
 535     SecBufferDesc outbuf_desc;
 536
 537     if (c->sizes.cbMaximumMessage == 0) {
 538         sspi_ret = QueryContextAttributes(&c->ctxt_handle, SECPKG_ATTR_STREAM_SIZES, &c->sizes);
 539         if (sspi_ret != SEC_E_OK)
 540             return AVERROR_UNKNOWN;
 541     }
 542
 543     /* limit how much data we can consume */
 544     len = FFMIN(len, c->sizes.cbMaximumMessage);
 545
 546     data_size = c->sizes.cbHeader + len + c->sizes.cbTrailer;
 547     data = av_malloc(data_size);
 548     if (data == NULL)
 549         return AVERROR(ENOMEM);
 550
 551     init_sec_buffer(&outbuf[0], SECBUFFER_STREAM_HEADER,
 552                   data, c->sizes.cbHeader);
 553     init_sec_buffer(&outbuf[1], SECBUFFER_DATA,
 554                   data + c->sizes.cbHeader, len);
 555     init_sec_buffer(&outbuf[2], SECBUFFER_STREAM_TRAILER,
 556                   data + c->sizes.cbHeader + len,
 557                   c->sizes.cbTrailer);
 558     init_sec_buffer(&outbuf[3], SECBUFFER_EMPTY, NULL, 0);
 559     init_sec_buffer_desc(&outbuf_desc, outbuf, 4);
 560
 561     memcpy(outbuf[1].pvBuffer, buf, len);
 562
 563     sspi_ret = EncryptMessage(&c->ctxt_handle, 0, &outbuf_desc, 0);
 564     if (sspi_ret == SEC_E_OK)  {
 565         len = outbuf[0].cbBuffer + outbuf[1].cbBuffer + outbuf[2].cbBuffer;
 566         ret = ffurl_write(s->tcp, data, len);
 567         if (ret < 0 || ret != len) {
 568             ret = AVERROR(EIO);
 569             av_log(h, AV_LOG_ERROR, "Writing encrypted data to socket failed\n");
 570             goto done;
 571         }
 572     } else {
 573         av_log(h, AV_LOG_ERROR, "Encrypting data failed\n");
 574         if (sspi_ret == SEC_E_INSUFFICIENT_MEMORY)
 575             ret = AVERROR(ENOMEM);
 576         else
 577             ret = AVERROR(EIO);
 578         goto done;
 579     }
 580
 581 done:
 582     av_freep(&data);
 583     return ret < 0 ? ret : outbuf[1].cbBuffer;
 584 }
 585
 586 static int tls_get_file_handle(URLContext *h)
 587 {
 588     TLSContext *c = h->priv_data;
 589     return ffurl_get_file_handle(c->tls_shared.tcp);
 590 }
 591
 592 static const AVOption options[] = {
 593     TLS_COMMON_OPTIONS(TLSContext, tls_shared),
 594     { NULL }
 595 };
 596
 597 static const AVClass tls_class = {
 598     .class_name = "tls",
 599     .item_name  = av_default_item_name,
 600     .option     = options,
 601     .version    = LIBAVUTIL_VERSION_INT,
 602 };
 603
 604 const URLProtocol ff_tls_protocol = {
 605     .name           = "tls",
 606     .url_open2      = tls_open,
 607     .url_read       = tls_read,
 608     .url_write      = tls_write,
 609     .url_close      = tls_close,
 610     .url_get_file_handle = tls_get_file_handle,
 611     .priv_data_size = sizeof(TLSContext),
 612     .flags          = URL_PROTOCOL_FLAG_NETWORK,
 613     .priv_data_class = &tls_class,
 614 };